PROBLEM TO BE SOLVED: To improve uniformity of the amount of light in a plane parallel to a culture medium surface over a range of a length where a seedling grows when the seedling is grown using a lighting device, to reduce dispersion of seedling growth, and to enhance the space utilization factor during the raising of the seedling.SOLUTION: Each prism sheet 35 is disposed in a part of a region of a light emitting surface along the edge of a light guide plate in the lighting device for raising a plant having the light guide plate 31 and a light source 20 disposed in at least one end of the light guide plate so that the prism direction is parallel to the edge. Two prism sheets are overlapped in four corners of the light guide plate so that the prism directions intersect at right angles. Light diffusing from the central part where the prism sheet is not disposed is controlled so as to face in the direction intersecting the light emitting surface of the light guide plate at right angles in the region where the prism sheets are disposed without reducing the amount of light.COPYRIGHT: (C)2012,JPO&INPIT【課題】照明装置を用いて苗を生育させる際に、苗の生長する長さの範囲に亘って、培地面と平行な面内の光量の均一性を向上させて、苗生育のばらつきを低減することおよび苗育成時の空間利用率を高めること。【解決手段】導光板31と、導光板の少なくとも一端に配置された光源20とを有する植物育成用照明装置の、導光板の縁部に沿った光出射面の一部の領域に、プリズム方向と縁部と平行になるようにプリズムシート35を配置する。導光板の四隅は、2つのプリズムシートをプリズム方向が直交するように重ねる。プリズムシートが配置されない中央部から拡散する光は、光量を減じることなくプリズムシートが配置された領域で、導光板の光出射面と直交する方向を向くように制御される。【選択図】図1
